The conventional method of orthodontic tooth movement, as practiced in the prior art, has been one of constant pressure applied to the tooth in order to move the tooth through the adjacent bone. Constant pressure applied to the periodontal membrane by traditional orthodontic appliances causes the periodontal fibers to become cell-free which results in stand-still of the tooth. Compression of tissue results in reduced blood supply and tissue necrosis, and the tooth will not move again until the bone subjacent to the hyalinized tissue has been eliminated by undermining resorption. Generally, it is essentially the magnitude of the force which will determine the duration of the hyalinization. Moreover, strong forces produce a wide hyalinization area of long duration. A discussion of this phenomena may be found on pages 76 and 97 of Current Orthodontic Concepts and Techniques, T. M. Graber, Editor, published by W. B. Saunders & Co., 1969.
When a tooth is tipped by a continuous force exerted on it by a usual prior art orthodontic appliance, the periodontal membrane is compressed in a circumscribed area situated close to the alveolar crest. This area becomes cell-free and the blood vessels are occluded, and oesteoclastic activity is reduced to a minimum. A description of this occurrence may be found, for example, at page 497 of Orthodontic Principles and Practice by Graber, Second Edition, published by Saunders & Co., 1967. If the pressure area of the periodontal membrane during the movement of a tooth by an orthodontic device is not compressed by strong forces, then the formation of oesteoclasts, the cells responsible for resorption of bone, will be enhanced. The flow of blood to the area will not be restricted, and consequently oesteoclastic activity will be more vigorous and bone resorption will be increased.
As stated above, the orthodontic appliance of the present invention introduces pressure impulses to the tooth being moved, rather than a continuous force. With every pressure impulse from the appliance of the invention, the tissue pressure in the periodontal membrane and adjacent bone tissue will be increased. When the pressure is relaxed, the tissue pressure in the peridontal membrane and adjacent bone tissue will be reduced. This fluctuation from high pressure to low pressure in the periodontal and adjacent tissue will result in a pump-like action that will suck blood and tissue fluid into the area, and will then expel fluid from the area, for each cycle of operation. This serves to increase the cellular action around the moving tooth, giving rise to more oesteoclasts for bone resorption and more oesteoblasts for bone apposition.
The active exchange of fluid during the pulsating operation of the appliance of the invention helps carry the by-products of bone resorption out of the resorption area. The pulsating tooth movement produced by the appliance of the invention is physiological and dynamic in nature, rather than pathological. Because the pulsation pressure exerted by the appliance of the invention does not result in areas of hyalinization and necrosis, there is no root resportion or horizontal bone loss during the operation. The pump-like action of the tooth being pulsated by the appliance of the invention is the same on the tension side of the tooth as on the compression side, but opposite in the timing cycle. On the tension side of the tooth, the increased blood supply results in increased cellular activity. The bone building cell is the oesteoblast. The oesteoblastic activity acts in a maximal manner during pulsating tooth movement, resulting in increased bone formation and active stabilization.
To reiterate, pulsation pressure optimal in magnitude and frequency, as produced by the appliance of the invention, is the ideal force for tooth movement because blood supply to the adjacent tissue is not reduced, but due to cyclic positive and negative tissue fluid pressures, a pump-like action is set up in the tissue creating greater blood supply. This enhanced blood supply results in increased oesteoclastic cellular action for the resorption of bone and increased oesteoblastic cellular action for the deposition of new bone elements. Greater tissue exchange in the area of tooth movement to enhance the removal of bone breakdown products, and to enhance the supply of elements necessary for the formation of new bone; and little or no areas of hyalinization or necrosis of tissue, so that root resorption by cementum necrosis does not occur.
The pulsation or vibrational nature of the force applied to the tooth by the appliance of the invention also helps to break down tissue resistance, as mentioned above. The fibrous elements of the adjacent tissue tend to give way more easily to the moving tooth mass, as the tooth is vibrated, and the tooth moves along the path of least resistance. The vibrating tooth mass more easily separates the fibrous elements and moves more easily through the adjacent bone. The increased circulation and vibrational effect occurs not only in the local area, but flows to adjacent tissues to aid in their adjustment, as teeth are moved through bone, and the total boney architecture is changed.
As a result, the use of the pulsating orthodontic appliance of the present invention results in faster movement of the tooth; reduction of root resorption during orthodontic movement; reduction of horizontal bone loss during bone reconstruction; reduced discomfort from heavy orthodontic pressures; and reduction in tooth extrusion from their boney sockets when pressurized.
The total effect resulting from the use of the orthodontic appliance of the invention is that tooth movement is of a physiological nature causing little or no irreversible results to the tooth or horizontal bone level, and expediting the travel of the tooth along its path through the adjacent bone so as to obtain the most rapid orthodontic movement in a painless environment.
Most orthodontic problems of dental protrusion and/or tooth size arch length discrepancies can be corrected by the use of the pulsating appliance of the present invention. Moreover, the conventional therapy of bicuspid extraction is eliminated when the appliance of the invention is used and, instead, third molars may be extracted and all posterior teeth moved distally.